Question -
Answer -
Inner radius of the toroid, r1 =25 cm = 0.25 m
Outer radius of the toroid, r2 =26 cm = 0.26 m
Number of turns on the coil, N =3500
Current in the coil, I =11 A
(a) Magneticfield outside a toroid is zero. It is non-zero only inside the core of a toroid.
(b) Magneticfield inside the core of a toroid is given by the relation,
B = 
Where,
= Permeability of free space =
l =length of toroid
(c) Magneticfield in the empty space surrounded by the toroid is zero.